The present invention relates to systems that supply a partial vacuum and pressurized air primarily for medical and dental facilities. In a dentist's office, for example, a partial vacuum is used to remove saliva, tissue, rinse liquids, and tooth filling particles from a patient's mouth. Pressurized air is required for pneumatic dental tools such as high speed drills, and for clearing a localized area of a patient's mouth for examination or treatment.
The state of the art heretofore in this field is represented by the teachings of U.S. Pat. Nos. 3,734,122 and 5,222,871. In each of these patents, a partial vacuum is provided by a liquid ring vacuum pump and pressurized air is provided by one ('122) or two ('871) reciprocating piston compressors. Each pump and compressor is described as being provided with a corresponding electric motor, so the '122 apparatus requires two such motors and the '871 apparatus requires three.
A liquid ring vacuum pump utilizes a high speed impeller that swirls water in a housing to create a positive seal and to remove air from the housing creating a partial vacuum, hereinafter referred to only as a "vacuum." This type of pump requires a constant supply of water to generate a vacuum and to remove heat from the pump. A water supply and drain must therefore be readily available before installing a liquid ring system. Water use is of course an important environmental as well as economic factor in many areas. A typical liquid ring vacuum pump consumes 30 gallons of water per hour. Therefore, such a pump operating 40 hours per week will consume 60,000 gallons of water in a 50 week working year.
Even with a water recycling unit installed, liquid ring pumps require some 10,000 gallons of water annually. Furthermore, recycled water will inevitably pick up contaminants as the water is recirculated through a liquid ring pump, tending to make the water somewhat abrasive. The resulting "gray water" is known to reduce the life of the pump's seals and therefore increases the maintenance requirements and operating costs of a liquid ring pump.
The systems of the '122 and '871 patents further require multi-level frames for minimizing the footprint requirements of the numerous system components. The '122 patent discloses an upright two-level cabinet-type frame having a liquid ring vacuum pump mounted in the base thereof and a compressor mounted on a platform suspended from the top of the cabinet. The compressor drive motor is mounted to the underside of the platform and the pump drive motor is mounted in the base of the cabinet.
The '871 patent describes an upright three-level frame in which the two compressors and their respective motors are mounted on the upper-most level of the frame. A liquid ring pump and its drive motor are mounted on the middle level, and an air receiving tank is positioned on the lower level.
Access to the components of the systems described in these patent is restricted by placement of the components in upright frames. A technician must therefore reach through the frame, possibly while on a ladder, to obtain access to and service the system components. Furthermore, the placement of heavy components such as pumps, compressors, and their respective drive motors at intermediate or upper levels within the frame tends to make such a system top heavy and certainly unstable in any situation that requires transport or relocation of the frame.
In response to the hereinbefore described problems, it is an object of the present invention to provide vacuum and compressed air utilities in a dental or medical facility from a single "frameless" reciprocating piston device and electric motor. The reciprocating piston device's crankcase and cylinders provide attachment points for all necessary controls and related system accessories. This improvement reduces the number of required components, avoids the need for a multilevel frame or cabinet, and further reduces the corresponding floor space requirements for the system.
It is a further object of this invention to provide an apparatus that delivers high vacuum levels without using large amounts of water.
It is a further object of the present invention to provide an apparatus that supplies dry compressed air without the need for an air drier.
It is a still further object of the present invention to provide such apparatus with support for the motor driving the reciprocating piston device that automatically adjusts the tension in a drive belt between the motor and the device as the belt stretches.
It is a still further object of the present invention to provide such an apparatus that is reliable, easy to service, and economical to purchase and operate.